1. Field
Example embodiments relate to a capacitor, a method of forming the same, and a method of manufacturing a semiconductor device including the same. More particularly, example embodiments relate to a capacitor having high capacitance, a method of forming the same, and a method of manufacturing a semiconductor device including the same.
2. Description of the Related Art
As semiconductor devices have been highly integrated, a unit cell thereof may have a reduced area. Because driving capacity of a dynamic random access memory (DRAM) depends on capacitance of a capacitor, research on increasing capacitance of a capacitor with a reduced area have been performed.
Generally, capacitance of the capacitor is proportional to an effective area thereof and to a dielectric constant of a dielectric layer, and inversely proportional to a thickness of the dielectric layer. Thus, a cylindrical capacitor may be used in order to increase the effective area of the capacitor. Additionally, the dielectric layer of the capacitor may be formed to have a thin thickness and of a high-k material.
However, since a conventional cylindrical capacitor may have a high aspect ratio, adjacent cylindrical capacitors may lean on each other when a mold layer for forming the capacitors is removed, and thus, 2-bit fail may occur. Additionally, a lower electrode of the conventional cylindrical capacitor may not be formed by a single process because of the large height thereof. Furthermore, the dielectric layer of the conventional cylindrical capacitor may not be formed on a lower portion of the lower electrode because of the high aspect ratio.
FIG. 1 illustrates a schematic perspective view of conventional cylindrical capacitors on a vertical metal-oxide-semiconductor (MOS) transistor. For example, as illustrated in FIG. 1, the conventional cylindrical capacitors may not be formed by a single process because of the large height thereof, and adjacent capacitors may lean on each other so that 2-bit fail may occur, e.g., upper portions of adjacent cylindrical capacitors may contact each other as illustrated in FIG. 1 Additionally, the cylindrical capacitor may have a high aspect ratio, and thus, forming a dielectric layer with a uniform thickness throughout the, e.g., entire, lower electrode may be difficult due to a high thickness of the dielectric layer at an entrance of the lower electrode.